Arjuna did not require the instruction of Bhagavad-gītā. He was already enlightened, but he presented himself as a fool just to induce the Lord to speak on Bhagavad-gītā, and it is noted by Vyāsadeva, Vedavyāsa, in the Mahābhārata, so that people may take advantage of the instruction of the Supreme Personality of Godhead. Everything is there: what is this brahma-jyotir, what is this material world, what is that spiritual world, what is our object of life, what we should know.
But we are . . . because we are so much influenced by the material world, especially in this age of Kali, the age of misunderstanding and quarreling, that people are mandāḥ sumanda-matayo manda-bhāgyā hy upadrutāḥ (SB 1.1.10). Prāyeṇālpāyuṣaḥ kalāv asmin yuge janāḥ. In this age their life is very short. Span of life is very short. And manda, all bad, not good men. Manda. And even there are so-called good men, they have got their own process of knowledge, speculative process. Godless. The main basic principle of speculative process is to avoid Kṛṣṇa, to avoid God. There are so many commentaries on Bhagavad-gītā to make Kṛṣṇa nil. That is mental speculation. Somebody is saying that in the Bhagavad-gītā there is karma only recommended. Somebody says jñāna. Somebody says yoga. Somebody says bhakti. But actually Bhagavad-gītā is meant for bhaktas. Bhakto 'si sakhā ceti (BG 4.3). Bhagavad-gītā was instructed to Arjuna for his only qualification, that he was a devotee of Kṛṣṇa. Bhakto 'si me sakhā ceti.